Extreme Pareto - 1% of perpetrators commit 63% of the crimes.

From The 1% of the population accountable for 63 % of all violent crime convictionsby Orjan Falk, Marta Wallinius, Sebastian Lundstrom, Thomas Frisell, Henrik Anckarsater, and Nora Kerekes.

From the Abstract:

A total of 93,642 individuals (3.9%) had at least one violent conviction. The distribution of convictions was highly skewed; 24,342 persistent violent offenders (1.0% of the total population) accounted for 63.2% of all convictions. Persistence in violence was associated with male sex (OR 2.5), personality disorder (OR 2.3), violent crime conviction before age 19 (OR 2.0), drug-related offenses (OR 1.9), nonviolent criminality (OR 1.9), substance use disorder (OR 1.9), and major mental disorder (OR 1.3).

Conclusions - The majority of violent crimes are perpetrated by a small number of persistent violent offenders, typically males, characterized by early onset of violent criminality, substance abuse, personality disorders, and nonviolent criminality.

I cam across this in the recent reporting of the most prolific rapist in British history. He was believed to have committed sexual assault against at least 190 men.

The research above combined with the fact that the perpetrator was an Indonesian PhD student prompts a thought.

It is striking that the Anglophone nations in particular but also the cultures of northwestern Europe tend to be pretty open to emigration compared to most other countries and cultures. However, there is also much energy invested in debating immigration policies. The postmodernist left tends to characterize this, against all evidence, as racism and fear of the the other.

Which is largely nonsense given the historical openness to immigrants. Much of the debate entails concerns about perceived costs as the most immigrant receptive nations also tend to have relatively generous welfare states. As Milton Friedman once noted:

It's just obvious you can't have free immigration and a welfare state.

So, despite their cultural openness, the western open countries have invested heavily in managing their openness, trying to ensure that the immigrants admitted won't undermine the existing generous welfare systems.

There has also been a subtler and less vocal undercurrent as well which focuses on the limits of absorption. Just how many people of variant cultures can an established culture absorb without degradation or collapse. In more positive terms, how many immigrants can be absorbed and how quickly can they be locally acculturated without destroying the existing highly productive culture? It is a fair question but one which doesn't receive much attention.

But the case of the Indonesian student in Britain along with the 1% of perpetrators cause 63% of the crime introduces another possible consideration.

If crime (or any other negative outcome) is highly Pareto distributed, then there is a very high consequence to immigration screening. If you are able to effectively preclude all of the 1% of perpetrators, then you should be able to ramp up immigration to very high levels constrained only by absorption rates.

If, however, you are not able to preclude the 1% of perpetrators, then the horrific consequence of that 1% will markedly constrain openness.

Not because of racism but because of simple bayesian risk aversion.

And if you immigrant pool has an excess of the 1%, then you are guaranteed to start generating native opposition to immigration. Why might there be an excess? Well, as a consequence of negative differentials. The positive outcomes for immigrants for moving from low efficiency economies to high efficiency economies are pretty obvious. Their economic return is very high even though there are financial, emotional, and professional costs to immigration.

But there is a negative calculation as well. If you are a political dissident or LGBT or a minority in your native country, discrimination might not be a matter of social disdain but can entail death, jail or being thrown from rooftops. Escaping such oppression is existentially beneficial.

But there is a third category. If you are deviant perpetrator such as a rapist, and you live in a country which executes rapists, then of course there is a great incentive to immigrate to low punishment countries. This incentive to immigrate taints the immigrant candidate pool by driving up the percentage of deviance. It is further exacerbated by yet another unplanned dynamic. Most receiving countries screen for competency. They are trying to select only the best and the brightest. So very bright rapists have a huge incentive to flood the immigrant pool. And if selected, they are the very perpetrators who, because of their brightness and capability, are least likely to be caught.

I am exaggerating the description of the dynamics to convey the meaning but when thought of this way, it makes clearer why there might be resistance to immigration in an environment where there is low trust in government competency to effectively screen and where there is a high consequence to failure and in a system where the candidate immigrant pool might have a disproportion of perpetrators.

Is this a real consideration. I doubt very much that it is a conscious one but I wouldn't dismiss it as an unarticulated concern.

Especially when you consider virtually all negative consequences to immigration fall almost completely on the bottom two quintiles of the native population.